difficult dressing

• 难选

difficult dressing的用法和样例：

例句

1. It is difficult to concentrate for Arsenical gold Mineral.
   含砷金矿属难选矿石。
2. Primary gold ore from Bangi, Guizhou, belongs to a clastic-type, finely disseminated, refractory particles.It is difficult to extract gold from the ore by cyanide infusing.
   贵州板其原生金矿石属碎屑岩类微细浸染型难选冶矿石，在氰化浸出之前需进行预处理。